A "super-for" loop

[Jason Quinn]

Frequently when programming, situations arise for me where I need a
nested number of for-loops. Such case arose for me again just
recently while I was inventing a dice game. Anyway, here is the
implementation that I ended up using to create a "super-for" loop in
AWK (a little trickier than C).

This simple example merely lists all possible outcomes of rolling 4,
6, 8, 10, 12, and 20 sided dice at once. A super-for loop requires an
array to specify the loop indices... here we have 6 dice and the
number of sides determines the indices. The code is easily modified
for an arbitrary number of dice (which is the whole point).

I identify three parts of a super-for which I called the prologue,
body, and epilog. Under most circumstances, I think the main body only
would get used.

I invite you to show off your AWK skills by improving the code if I
made any silly choices.

Cheers,
Jason

#shows an example of a superfor loop
BEGIN {
#define loop maximums
loopmax[1]=4
loopmax[2]=6
loopmax[3]=8
loopmax[4]=10
loopmax[5]=12
loopmax[6]=20
#call the loop
superfor(6)
}

#call the function as superfor(loopdepth). the zz is a local variable.
function superfor(loopdepth, zz) {
currloopnum++

#start of prologue
#end of prologue

for(loopcounter[currloopnum]=1; loopcounter[currloopnum]<=loopmax
[currloopnum]; loopcounter[currloopnum]++) {
if ( loopdepth==1 ) {
#start of superfor body
for (zz=1;zz<=currloopnum;zz++) {
printf loopcounter[zz] FS
}
print ""
#end of superfor body
}
else if ( loopdepth>1 )
superfor(loopdepth-1)
}

#start of epilog
#end of epilog

loopdepth++ ; currloopnum--
}

[Janis Papanagnou]

Jason Quinn wrote:
> Frequently when programming, situations arise for me where I need a
> nested number of for-loops. Such case arose for me again just
> recently while I was inventing a dice game. Anyway, here is the
> implementation that I ended up using to create a "super-for" loop in
> AWK (a little trickier than C).
>
> This simple example merely lists all possible outcomes of rolling 4,
> 6, 8, 10, 12, and 20 sided dice at once. A super-for loop requires an
> array to specify the loop indices... here we have 6 dice and the
> number of sides determines the indices. The code is easily modified
> for an arbitrary number of dice (which is the whole point).
>
> I identify three parts of a super-for which I called the prologue,
> body, and epilog. Under most circumstances, I think the main body only
> would get used.
>
> I invite you to show off your AWK skills by improving the code if I
> made any silly choices.

Well, a bit long-winded, maybe; certainly no silly choices you made.

But I suppose your algorithm will get slightly better comprehensible
if you make 'currloopnum' a parameter of the recursive function call.
(Using shorter names in this specific case of a small function might
make it easier to overview the operation done. YMMV.) And the split
is just another minor goodie added. It's basically your program that
you see below, I haven't changed much of the core of your algorithm.

BEGIN { n = split ("4 6 8 10 12 20", upb) ; multifor(n, 1) }

function multifor (depth, lno, nn)
{
for (lc[lno]=1; lc[lno]<=upb[lno]; lc[lno]++)
{
if (depth > 1)
multifor(depth-1, lno+1)
else
{
for (nn=1; nn<=lno; nn++)
printf("%s", lc[nn] FS)
print ""
}
}
}

Janis

[Jason]

On Mar 18, 7:45 pm, Janis Papanagnou <janis_papanag...@hotmail.com>
wrote:

> But I suppose your algorithm will get slightly better comprehensible
> if you make 'currloopnum' a parameter of the recursive function call.
> (Using shorter names in this specific case of a small function might
> make it easier to overview the operation done. YMMV.) And the split
> is just another minor goodie added. It's basically your program that
> you see below, I haven't changed much of the core of your algorithm.

Great. It's always interesting to see how others would have done
something.

Jason

[Aharon Robbins]

In article <49270fa7-376c-4751...@13g2000yql.googlegroups.com>,

Jason Quinn <jason.l...@gmail.com> wrote:
>#call the function as superfor(loopdepth). the zz is a local variable.
>function superfor(loopdepth, zz) {
> currloopnum++
>
> #start of prologue
> #end of prologue
>
> for(loopcounter[currloopnum]=1; loopcounter[currloopnum]<=loopmax
>[currloopnum]; loopcounter[currloopnum]++) {
> if ( loopdepth==1 ) {
> #start of superfor body
> for (zz=1;zz<=currloopnum;zz++) {
> printf loopcounter[zz] FS
> }
> print ""
> #end of superfor body
> }
> else if ( loopdepth>1 )
> superfor(loopdepth-1)
> }
>
> #start of epilog
> #end of epilog
>
> loopdepth++ ; currloopnum--
> }

I think this would make a great application for indirect function calls:

function superfor(loopdepth, prologue, body, epilogue, zz)
{
currloopnum++

@prologue()

for(loopcounter[currloopnum]=1; loopcounter[currloopnum]<=loopmax [currloopnum]; loopcounter[currloopnum]++) {
if ( loopdepth==1 ) {

@body()

}
else if ( loopdepth>1 )
superfor(loopdepth-1)
}

@epilogue()

loopdepth++ ; currloopnum--
}
--
Aharon (Arnold) Robbins arnold AT skeeve DOT com
P.O. Box 354 Home Phone: +972 8 979-0381
Nof Ayalon Cell Phone: +972 50 729-7545
D.N. Shimshon 99785 ISRAEL